Health changes during Covid-19: a nationwide study with dental students

ABSTRACT OBJECTIVE To assess the changes in stress levels, social behavior, dietary and parafunctional habits, oral hygiene, among other conditions perceived by dental students in Brazil during the Covid-19 pandemic and evaluated the correlations between stress level and other variables. METHODS An online questionnaire was developed and validated. Undergraduates enrolled in private and public dental schools were recruited by convenience sampling. Data were collected on the perceived changes regarding stress levels, financial and social characteristics, dietary habits, oral hygiene, health conditions, and parafunctional habits. Quantitative variables were expressed as absolute and relative frequencies. Wilcoxon test evaluated comparisons between perceived changes, and correlations between changes in stress levels and other variables were analyzed by Spearman correlation (α = 0.05). RESULTS A total of 638 dental students, mean age of 22.95 ± 4.10 years, participated in the study. During the pandemic, the reported stress levels increased while household income decreased (p < 0.05). Late dinners and mindless eating increased in frequency, whereas oral hygiene decreased (p < 0.05). Most of the health conditions and parafunctional habits assessed changed (p < 0.05). Perceived stress levels showed poor negative correlations with household income (rS = −0.14), poor positive correlations with the pressure to contribute financially in the household (rS = 0.19), and poor positive correlations with food choice frequency (rS = 0.15) (p < 0.05). CONCLUSIONS Dental students reported perceived changes in stress levels, dietary habits, oral hygiene, health conditions, parafunctional habits, and social behavior. Moreover, the results showed poor correlations, as students with higher stress levels tended to have the lowest household income, feel pressured to contribute financially in the household, and present a high meal intake frequency.


INTRODUCTION
Historically, several infectious disease outbreaks have taken place around the world, bringing significant consequences for humanity 1 . In 2019, news reported the first cases of Covid-19, caused by the new SARS-CoV-2 virus 2 . Due to its severity and rapid contagion spread, the World Health Organization (WHO) declared Covid-19 an international public health emergency and a pandemic 3,4 .
Its fast transmission rate, relevant medical complications, and high associated morbidity led to the proposition of several sanitary measures by infectiologists and world health authorities. Among those put in place to stop Covid-19 dissemination, social distancing proved the most challenging 3,5 .
A large portion of the world population went into quarantine, sequestered in their homes, which led to strict adaptations of daily habits and exacerbated changes in social dynamics 6 . Studies have shown that psychological disorders caused by social distancing, regardless of socioeconomic class, highly affect youth, known to have a greater need for socialization 3,7 .
The risk of imminent contamination, the uncertainty of its duration, the consequent financial losses, and several other factors related to the Covid-19 pandemic caused natural psychological responses like depression, anxiety, stress, and panic disorders to situations of sudden random changes 7 . Such negative emotions can lead to immunosuppression, which has deleterious health consequences 8 .
Moreover, psychological factors influence muscle hyperactivity, resulting in temporomandibular disorders and parafunctional activities such as clenching and bruxism 9 . Behavioral changes can also trigger eating disorders, alcoholism, changes in sleep rhythm, among other conditions that culminate in oral health problems 10 . Besides, studies show that the rates of inadequate, compulsive, or less healthy dietary habits increased throughout the pandemic 11 .
The severity of Covid-19 presented clear challenges for dentistry, considering the high chances of contamination due to patient proximity and the aerosols generated during clinical procedures 12 . Consequently, dental schools in Brazil had to suspend their in-person classes and training, thus implementing an emergency remote education system until the schools could reopen safely. Dental education is a demanding field and relies greatly on on-site instruction and hands-on practice for acquiring the necessary clinical skills 13,14 . In this pandemic scenario, dental students have been particularly affected by anxiety associated with learning complex clinical procedures and managing busy and challenging academic schedules 15,16 .
Other countries have investigated the psychological and financial impact of the Covid-19 pandemic on dental students 17,18 . A recent study conducted with Brazilian dental undergraduates found a high prevalence of alcohol abuse and anxiety during the pandemic 19 . But further information on behavioral and health changes is still missing. Thus, this study sought to assess the perceived changes in stress levels, dietary habits, oral hygiene, health conditions, parafunctional habits, and social behavior during the Covid-19 pandemic among Brazilian dental undergraduates. A second objective was to correlate stress levels with the other variables evaluated. Our null hypothesis posited that no perceived changes and no correlations regarding all variables would be found.

METHODS
We designed a nationwide quantitative, observational, cross-sectional survey, which was approved by the local Ethics Committee and registered in the Open Science Framework (OSF) database (doi: 10.17605/OSF.IO/48YUG). This study complied with all provisions of the local oversight committee guidelines on human subjects and HUCFF-UFRJ policies (protocol 4.422.128). This report followed the Survey Reporting Guideline (SURGE) 20 .

Sample Calculation and Participant Selection
Considering the 600936 students enrolled in 553 dental schools in Brazil 21 , we calculated the sample size at a 50% accuracy, 95% confidence interval and a 4% margin of error, using G*Power 3.1.9.2 software (Heinrich Heine, Universität Düsseldorf, Dusseldorf, Germany), resulting in a minimum survey respondent sample of 600 participants.
Based on a convenience sampling method, we emailed students enrolled in private or public dental schools from all five regions of Brazil (North, Northeast, Midwest, Southeast, and South). Eligibility criteria consisted of people of all ages, genders, and socioeconomic statuses. Only participants who failed to provide their written informed consent were excluded from the study.

Questionnaire Description
We developed an initial set of items based on seven domains: sociodemographic characteristics (program year, region, gender, age and household income); perceived stress levels; dietary behaviors (meals and food choices); oral hygiene; health conditions (gingivitis, tooth wear, pains, ulcers and herpes); parafunctional habits (clenching, grinding and nail, object, finger and lip biting); and social behaviors (sleep hours and alcohol consumption).
Paired experts from the following seven fields of knowledge analyzed the items for possible flaws and suggestions: social work, cariology, temporomandibular dysfunction, stomatology, nutrition, periodontics, and psychology. We calculated the agreement rate (%) between experts for each domain. Each item was individually validated by calculating the Content Validity Index (CIV). Expert agreement rate was 100% for all domains. CIV was 1 for all items, except for items 9, 10, 13, and 14, which had a CIV of 0.5. After adjustments and a new evaluation, these items reached a CIV of 1.
Subsequently, we performed a pretest with 32 randomly selected dental students. They were asked to determine item intelligibility and make relevant suggestions. Items 8,9,10,11,12,22,23,and 24 were adjusted based on their answers, after which the questionnaire was considered validated and ready to be applied.
Responses were collected from January to April 2021 and tabulated.

Statistical Analysis
Data collected via the online questionnaire were analyzed using BioEstat 5.3 (BioEstat, Belém, Brazil). Descriptive analyses were expressed in absolute and relative frequencies (%). As data collected on stress levels failed to meet the threshold for normality (Shapiro-Wilk test; p < 0.05), we adopted nonparametric methods. Within-subjects comparison between participants' perceptions before (past self-report) and during the pandemic for the ordinal variables (monthly household income, stress levels, food choice frequency, tooth brushing frequency and tooth brushing time) was calculated by Wilcoxon test. Within-subjects comparison between participants' perceptions before (past self-report) and during the pandemic for the categorical variables (meals, food choice, health conditions and parafunctional habits) was estimated by McNemar test. Spearman correlation was used to analyze correlations between changes in stress levels and the other variables. Significance level was set at 5%.

RESULTS
A total of 638 dental undergraduates answered the survey, of which 48.4% were fourthand fifth-year students, whereas 51.6% were approaching graduation. Regarding dental school, 23.1% of the participants were enrolled in private institutions and 76.9% in public dental schools. Age ranged from 17 to 67 years old, with mean age of 22.95 ± 4.10 years. Table 1 summarizes the distribution of respondents according to sociodemographic and educational characteristics. Table 2 presents the absolute and relative frequencies (%) of perceived changes in variables associated with the pandemic. Up to 69.8% of the students admitted feeling pressured to financially contribute in their household, showing a poor correlation to senior students (r S = 0.14, p = 0.0006) and a fair correlation to students living with reduced household income (r S = −0.28, p < 0.0001). Moreover, feeling pressured to contribute financially showed a poor correlation to higher stress levels (r S = 0.19, p < 0.0001).   Table 3 shows the median, lower quartile (Q 1 ) and upper quartile (Q 3 ) of ordinal variables. During the pandemic, household income decreased while the perceived stress levels increased (p < 0.0001). Regarding oral hygiene, participants changed their usual tooth brushing time (p = 0.0054), and the brushing frequency decreased (p < 0.0001). During the pandemic, participants reduced breakfast (p = 0.0261), lunch (p = 0.0192), and dinner (p < 0.0001) meals from their everyday dietary habits while adding late dinner and mindless eating (p < 0.0001). As for food choices, consumption of sugar-rich foods with low tooth adhesion (p < 0.0001), fat-rich foods (p = 0.0003), and tooth-staining foods (p = 0.0489) decreased. Moreover, the frequency in choosing these types of food increased during the pandemic (p < 0.0001). Results show a poor correlation between higher stress levels and a higher food choice frequency during the pandemic (r S = 0.15, p < 0.0001).
The number of participants who did not manifest signs or symptoms of health conditions decreased during the pandemic (p < 0.0001), whereas all signs or symptoms increased (p < 0.05), excepting herpes labialis (p = 0.1250). Similarly, the number of participants who did not manifest parafunctional habits before the pandemic researched zero during the pandemic (p = 0.0002). Bruxism (p < 0.0001) and lip biting (p = 0.0002) significantly increased, whereas nail and finger biting showed no significant statistical difference (p > 0.05).
Moreover, most participants noticed a change in their sleeping habits during the pandemic. Almost a quarter of the participants reported reducing their alcohol consumption. We found no correlations between sleep changes or alcohol consumption and stress levels (p > 0.05).

DISCUSSION
As the negative consequences of the pandemic transcend physical damage 18 , we need further studies focused on correlating them to mental health and the degree of population psychological and behavioral impact 22 . The present study assessed whether the pandemic and the suspension of in-person activities affected dental students in Brazil. Given the significant increase in cross-sectional survey applications during the pandemic, we developed and validated a patient-centered questionnaire using a protocol to facilitate easy engagement.
Since the construct focused on perceived changes instead of on classifying or diagnosing diseases, we rejected the null hypothesis.
A recent study suggested an increase in stress among healthcare students during the pandemic 12 , corroborating our results. Of the 638 participants, 27% reported feeling extremely stressed during the pandemic, whereas only 2% felt such stress levels before it. Moreover, 70% of the respondents claimed they felt pressured to financially contribute in their household due to decreased monthly household income. The correlations found between high stress levels, feeling pressured, and low household income suggest an association between these variables. Discontinuity of the academic routine and uncertainty regarding the graduation date may have contributed to this result, since senior students tended to feel pressured, possibly due to their suddenly postponed after-graduation plans. Regarding dietary behavior, the frequency of main meals (breakfast, lunch, and dinner) significantly decreased while that of late dinners and mindless eating increased, finding that might be explained by changes in the students' daily routine. Food choice frequency also increased, showing a positive correlation with high stress levels. Studies show that stress negatively affects eating behavior through the reward system in the brain. Among other conditions, stress can lead to neurobiological adaptations that promote overeating 23 .
We also observed changes in food choice. Results showed a significant decrease in the consumption of sugar-rich foods with low tooth adhesion, fat-rich foods, and tooth-staining foods. Since maintaining a balanced diet could help strengthen immunity and prevent viral infections, people opted for healthier eating habits during the pandemic 24 . Conversely, a study conducted in Italy reported an increased consumption of chocolate, ice cream, and desserts, known as comfort foods 25 . This might be explained by differences in the inclusion criteria used. While Scarmozzino and Visioli 25 study sample included Italians at large, we specifically focused on Brazilian dental students, who may choose food based on what they know about consuming sugar-rich foods and its consequences on oral health.
Consuming sugar-rich foods reduces the pH and predisposes people to dental caries. Tooth brushing and flossing, in turn, are activities that prevent decay 26 . Surprisingly, our study found that tooth brushing frequency significantly decreased during the pandemic. A Brazilian study conducted with adults during the pandemic also found a decreased tooth brushing frequency: due to mask wearing, people were less concerned about their smiles 27 . Dental students, however, presumably know the importance of a healthy oral hygiene. Further studies are needed to understand this contradiction.
As a possible consequence of this decreased oral hygiene, all health conditions evaluated increased during the pandemic. Moreover, increased temporomandibular joint (TMJ) pain and tooth wear are concomitant with increased parafunctional habits. This finding may be associated with high-stress levels as psychological factors influence muscle hyperactivity and contribute to developing parafunctional activities 9 . These can lead to temporomandibular disorders, advanced tooth wear, and fracture of dental restorations and implants 28 .
Since the Covid-19 pandemic and its consequences could not be predicted, the present cross-sectional study is limited by the inclusion of questions regarding participants' perceptions prior to the pandemic. Although no cause-to-effect relationship between variables can be argued, this study suggests causal hypotheses so researchers can search for correlations during the pandemic. All correlations presented here were statistically significant, thus confirming adequate power of the sample size. Concomitantly, all correlations were considered either fair or poor 29 , which puts into question the clinical relevance of these findings and implies the need for further confirmation. To achieve a more representative study sample, we applied no age restrictions to the inclusion criteria, which resulted in a mean age of 22.95 and a range from 17 to 67 years old. Having only 3.1% of the participants aged thirty years or older could be considered a limitation, since young adults would probably perceive the impacts of the pandemic differently from older adults.
Importantly, monthly household income decreased while stress levels increased among dental students during the pandemic 30 . We also observed changes in social behaviors and dietary choices, decreased oral hygiene, increased signs and symptoms of health conditions, and increased parafunctional habits. High stress levels may be associated with increased meal frequency and the pressure to contribute financially in their household. Senior students and students from reduced household income may feel more pressured.